Although a number of prior art references are directed to testing local and remote subscriber lines, the references do not disclose or suggest a telephone tie line analyzer which can automatically test all tie trunk lines associated with a particular user at any desired time in a way which is easily programmable. In particular the following prior art references are known:
______________________________________ U.S. Pat. No. Inventor Date of Issue ______________________________________ 3,674,947 Chulak 1972 3,410,966 Davies 1968 3,571,530 Davies 1971 3,980,839 Hutcheson 1976 3,917,915 Karras 1975 4,021,624 Kelly et al 1977 4,029,913 Gunderson 1977 4,054,760 Morgen 1977 4,185,174 Beyhurst et al 1980 4,196,321 Bosik 1980 4,208,552 Castriotta et al 1980 4,255,625 Walton et al 1981 4,258,236 Conklin et al 1981 ______________________________________
U.S. Pat. No. 4,258,236, Conklin et al is of interest since it describes the type of service provided by telephone companies to test customer leased telephone lines. Each customer leased dedicated tie trunk line connects two locations of the customer and is classified as a voice grade four wire service; the four wires being a receive pair (tip and ring) and a transmit pair (tip and ring). These four wires pass through at least one telephone company central office and at each customer location, terminate in a so-called terminating unit where connection to customer installed equipment such as a computerized private branch exchange (PBX) is made.
To test these lines, the telephone company usually provides a loop-back test circuit in each terminating unit. These test circuits upon receipt of a 2713 Hz signal simultaneously disconnect the customer installed equipment from the terminating unit and respectively connect the receive and transmit tip wires together and the ring wires together through a loop-back amplifier. The 2713 Hz tone is generated at the telephone company central office.
This receipt of a loop-back 2713 Hz signal at the central office provides a continuity check of the four wire line. In addition a milliwatt test signal source at 1004 Hz and 0 db may then be connected to the four wire service to test the line for attenuation loss, distortion and noise. Once the tests are completed the four wire line is returned to service by a second tone received by the loop-back test circuits from the central office.
The above testing of leased telephone lines is not performed at times selectable by the customer and may not be done on a daily basis. Indeed, the customer has no independent verification of the test results until disruption of service occurs. The telephone company tests cannot be performed on an interval basis to monitor a line suspected to be faulty and do not test customer off premise extension lines, foreign exchange lines, and out-going WATS lines. All such tests and testing flexibility are performed by the present invention.
The Conklin et al patent describes testing procedures for data collection and/or processing equipment which are connected by modems and distribution and collection bridge pairs to the telephone lines. The lines are tested by transmitting a signal from a control circuit which disconnects the equipment at the remote location and provides quiet termination of the receive and transmit pairs. Another aspect of the disclosure provides a signal that connects a milliwatt signal source to the remote location transient pair. Multipoint testing when a plurality of modems are used at the remote location is also disclosed with each switching and testing circuit responsive to a different predetermined tone frequency. Conklin et al does not disclose or suggest a telephone line analyzer that can be user programmed to test any selection of user lines and does not disclose testing of off premise extension lines, foreign exchange lines and outgoing WATS lines. Conklin et al also does not disclose or suggest a device that reports all test results in a clear and concise manner and which can provide testing on a priority or interval basis.
U.S. Pat. No. 3,674,947, Chulak, discloses a remote testing system for communication circuits. It shows a prior art system (FIG. 1) and its system (FIG. 2), both for remote testing of subscriber lines. Its particular advantage as distinguished from that shown in its FIG. 1 is that only one connection through non-dedicated facilities of the switching network and of the lines connecting the locations need be made to set up the testing connection. The invention is directed to testing local telephone subscriber lines through the use of near end and far end switching equipment. It uses a near end answering tone and a far end timer to prevent accidental calls by third parties to the far end test number. It is a manual testing device unlike the present invention and consequently cannot automatically obtain or select a desired tie trunk line.
U.S. Pat. No. 3,410,966, Davies, is a system basically corresponding to that shown in FIG. 1 of Chulak, and again is directed to remote testing of telephone subscriber lines through a manual process.
U.S. Pat. No. 3,980,839, Hutcheson, describes a system for monitoring a Totalphone.TM. switching system. This system employs a microprocessor to monitor the operation of both the central office switching subsystem and the remote switching systems that are connected by means including a dedicated trunk line. It is directed to determining whether the switching system is operating properly and is not directed to analyzing attenuation losses on telephone lines.
U.S. Pat. No. 3,571,530, Davies, discloses a remotely controlled telephone loop testing system wherein signalling is performed over non-dedicated trunks. Although it uses multifrequency tone bursts to set up loop test circuits, it does not test dedicated tie trunk lines, but rather tests remote telephone subscriber lines.
The remaining cited references are of interest in showing various telephone switching and subscriber line testing, but none disclose or suggest an automatic telephone line analyzer for measuring and recording the attenuation on such lines associated with a particular user.